CVE-2021-39246

What it is

Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can compromise the privacy of visits to v2 onion addresses. Exact timestamps of these onion-service visits are logged locally, and an attacker might be able to compare them to timestamp data collected by the destination server (or collected by a rogue site within the Tor network).

At a glance

Exploitability

Can be exploited with physical access without logging in. High risk of data exposure, data tampering.

Exploit odds

0.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-09-24 19:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 04:03 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.5% in the next 30 days (EPSS).
• Severity: 6.1 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-09-24 19:15 UTC

Last modified

2026-06-17 04:03 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-532 · Secrets in logs

Record status

Modified

Affected

• Torproject Tor Browser ≤ 10.5.6
• Torproject Tor Browser 11.0

Attack profile CVSS 3.1 · 6.1

Attack vector

Physical

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-39246.md and follow it. Check whether this project is affected by CVE-2021-39246. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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